1. Field of the Invention
This invention relates generally to confirming proper communications within a network. In particular, this invention relates to creating a Line Trace byte to be placed in the Line Overhead portion of the Transport Overhead of a SONET STS-1 frame.
2. Related Art
A communication network serves to transport information among a number of locations. The information is usually presented to the network in the form of time-domain electrical signals and may represent any combination of telephony, video, or computer data in a variety of formats. A typical communication network consists of various physical sites, called nodes, interconnected by information conduits, called "links." Each link serves to carry information from one site to another site. Individual sites contain equipment for combining, separating, transforming, conditioning, and/or routing data.
Optical networks, in turn, typically include a plurality of fiber optic transmission lines or links permitting high bandwidth data communications used in telephone and other data network systems. High speed data can be modulated on light waves which are transmitted by optical sources (such as semiconductor diode lasers) through the optical network. The optical transmission line, connecting an optical transmitter and receiver, can propagate many light wave signals of different frequencies simultaneously.
These fiber optic communications links carry vast amounts of information among distant sites to accomplish data, voice and image connectivity over a large geographical area. Optical transmission lines, transmitters and receivers, however, are prone to failure. The failure of such links can have a substantial economic and practical impact on network users and network service providers. Therefore, in designing communications networks, special measures are practiced to assure utmost reliability of network components and survivability in the event of link failure due to physical fiber damage or optical component failure. Consequently, restoration techniques have been devised to circumvent a network link failure and to quickly restore normal traffic flow.
Today, the typical method of transporting optical data along an optical fiber network is through the use of a digital hierarchy called SONET. For a comprehensive summary of the state of the art concerning SONET, the reader is referred to "Telecommunications Technology Handbook," by Daniel Minoli, Artech House, Inc. (1991), which is incorporated by reference herein. In particular, Chapter 3.8 specifically addresses SONET signal applications. However, a brief description is provided here for the reader's convenience.
In order to provide for the transporting of large cross-sections of traffic, SONET establishes a set of network interface standards aimed at enabling global network interconnection. Additionally, SONET defines a multiplexing hierarchy ensuring equipment compatibility between different manufacturers. SONET handles fiber-based signals and allows for the extraction of low rate signals. In particular, SONET defines a hierarchy of rates and formats to be used by vendors, network service providers (or carriers), and end-users for optical transmission at and above the 51.840 Mb/s rate. The data comprises an electrical form of an 810-byte frame transmitted every 125 us to form the 51.840 Mb/s signal (also known as synchronous transport signal-level 1 or STS-1). At this rate, each of the constituent 8-bit bytes is equivalent to a 64 kb/s channel. For transmission over fiber spans, the optical counterpart of the STS-1 signal is called the optical carrier-level 1 signal (OC-1). For both of these signals, the last digit, 1, represents an associated byte-interleaved multiplex structure that creates a group of standard rates at N-times the STS-1 or OC-1 rate. For example, a data signal can be a STS-48 synchronous data signal bearing digital data at about 2.5 Gbps or the equivalent of 32 thousand telephone-quality voice channels.
Presently, optical networks carry high-data rate traffic supporting an ever-increasing variety and range of interconnected data networks, lower-level networks, distributed systems, consumer communication products and services, and remote units. As the proliferation and diversity of network elements and signals becomes greater, network management becomes even more critical. What is needed is a method to insure that SONET optical data signals are routed correctly through the network in order to avoid mis-connections and loss of service continuity.